Multichannel Temperature Sensor Based on Fiber Bragg Grating Combined With Fiber‐Cavity Ring‐Down Technique

ABSTRACT A multichannel fiber Bragg grating (FBG) temperature sensor based on use of the fiber ring‐down technique is reported. A quasi‐linear fiber‐optic cavity consisting of the FBG is used to perform the ring‐down measurement. Ring‐down signals acquired from two fiber cavities connected in series are combined simultaneously with a reference field to obtain heterodyne beat signals. Use of this heterodyne detection technique allows the sensor to perform highly sensitive and accurate temperature measurements. The sensor achieves a temperature resolution of 0.014°C.